1. Field of the Invention
The present invention relates to a developer replenishing apparatus for replenishing a developer replenisher to a developing apparatus for use in a copying apparatus, a facsimile apparatus, a printer or the like for developing an electrostatic image, formed on an image bearing member by an electrophotographic process or an electrostatic recording process with a developer thereby obtaining a visible image.
2. Related Background Art
In an image forming apparatus such as a copying apparatus, a facsimile apparatus, a printer or the like, there is well known a method of developing an electrostatic latent image by supporting a dry developer as an image developer material on a surface of a developer carrying member, carrying and supply the developer to the vicinity of a surface of an image bearing member which bears an electrostatic latent image and developing the electrostatic latent image under an application of an alternating (AC) electric field between the image bearing member and the developer carrying member, thereby obtaining a visible image, and, it is common to employ a developing sleeve as the developer carrying member and a photosensitive drum as the image bearing member.
For such image development, there is for example known so-called magnetic brush developing method which employs a developer of a two-component composition (so-called two-component developer) containing toner particles and carrier particles, to form a magnetic brush on the surface of a developing sleeve provided therein with a magnet, positions such magnetic brush in sliding contact with or in a close relationship to a photosensitive drum opposed across a small developing gap and continuously applies an AC electric field across a gap between the developing sleeve and the photosensitive drum (S-D gap) thereby repeating a transition of the toner particles from the developing sleeve side to the photosensitive drum side and a reverse transition thereof to achieve a development.
For example in an image forming apparatus utilizing the aforementioned two-component developer, as the toner is consumed with the progress of image formation, it is necessary to replenish the toner into the developing apparatus.
In the following there will be explained a configuration of a developing apparatus for two-component magnetic brush development and a developer replenishing apparatus for replenishing the developer into the developing apparatus, with reference to FIGS. 7A and 7B, which are a schematic cross-sectional views of the developing apparatus and the developer replenishing apparatus.
A developing apparatus 4 is provided, in a developer container (main body of the developing apparatus) 41, with a developing sleeve 46 as a developer carrying member, a magnet roller 47 as magnetic field generating means fixed inside the developing sleeve 46, a developing screw 44 and an agitating screw 45 serving as developer agitating means which agitates and carries the developer in the developer container 41, a toner receiving aperture 49, and a regulation blade 48 provided for forming a thin layer of the developer on the surface of the developing sleeve 46.
An interior of the developing container 41 is divided into a developing chamber 42 and an agitating chamber 43. The developing screw 44 is provided in the developing chamber 42, and the agitating screw 45 is provided in the agitating chamber 43. As shown in the illustration, the developing sleeve 46 is positioned close to the photosensitive drum 1, and is rotated in the same or opposite direction to the photosensitive drum 1, thereby executing a development in a state where the developer (hatched portion in the drawing) is in contact with the photosensitive drum 1.
A developer replenishing apparatus 50 is provided with a toner sub-container 51 for storing replenishing developer (toner) to be replenished to the developing apparatus 4. Above the toner sub-container 51, there is provided a toner supply aperture 60 capable of receiving a toner supply.
Also under the toner sub-container 51, a toner carrying pipe 52, capable of carrying the toner from the toner sub-container 51, is provided in a cylindrical shape protruding substantially horizontally. In the toner carrying pipe 52, a replenishing screw (first replenishing means) 53, having a spiral fin on a rotary axis, is provided in rotatable manner. The replenishing screw 53 is connected to drive means 54 which rotates the replenishing screw 53.
The toner sub-container 51 is also provided with a toner sensor (toner presence/absence detection sensor) 56 for directly detecting presence/absence of the toner by an optical method. Further, the toner sub-container 51 is also provided therein with an agitating member 55 capable of a rotating or reciprocating motion.
The developer replenishing apparatus 50 further includes a main toner container (second developer container) 57, provided above the toner sub-container 51, for storing the toner to be replenished to the toner sub-container 51. The main toner container 57 is provided therein with an agitating/carrying member (second replenishing means) 58 in rotatable manner, which is connected to drive means 59 which rotates the agitating/carrying member 58.
The main toner container 57 may be rendered detachable from the toner sub-container 51 and the main body of the image forming apparatus, and, in such case, it is called a toner cartridge (or toner bottle).
In the following, there will be explained an image forming operation in the developing apparatus.
The developing container 41 contains a two-component developer formed by a mixture of non-magnetic toner particles (toner) and magnetic carrier particles (carrier). A toner/carrier mixing ratio (hereinafter called T/C ratio) is maintained constant by a toner replenishment by an amount of the toner consumed in image development. More specifically, the toner is dropped, by the replenishing screw 53 from the toner sub-container 51 containing the replenishing toner, into the agitating chamber 43 provided with the agitating screw 45 through the receiving aperture 49 of the developing container 41 and thus replenished to the developing apparatus 4. For detecting and maintaining the T/C ratio of the developer in the developing container 41, there have been employed various methods.
In the following, there will be explained a toner replenishing operation into the toner sub-container 51 in case the toner therein decreases by toner consumption.
The agitating member 55 has a function of disintegrating toner by a rotating or reciprocating motion, in order to avoid toner blockage in the toner sub-container 51. Also the replenishing screw 53 is provided for executing a function of carrying the toner in the toner sub-container 51 in a longitudinal direction (direction parallel with the plane of drawing) toward the aperture 49 communicating with the developing container 41, and a function of extruding and dropping the toner from the aperture onto the developing container 41.
In case, after the detection of absence of toner by the toner sensor, a toner absent state continues even after the operation of the agitating member 55, it is judged that the toner is not solidified in a part of the toner sub-container 51 but the toner is really used up.
When the absence of toner in the toner container 51 is identified, the agitating/carrying member 58 in the main toner container 57 rotates to replenish the toner from the main toner container 57 to the toner sub-container 51. The agitating/carrying member 58 is provided for a function of disintegrating the toner by rotation thereby preventing blockage of the toner in the main toner container 57, a function of carrying the toner in the main toner container 57 in the longitudinal direction (parallel with the plane of drawing) toward the toner supply aperture 60 communicating with the toner sub-container 51, and a function of extruding and dropping the toner from the supply aperture 60 into the toner sub-container 51, and is generally constituted of a sheet material such as of PET.
The rotation of the agitating/carrying member 58 of the main toner container 57 is continued until the toner 56 detects presence of toner, and, thereafter, the toner replenishment is executed in succession from the toner sub-container 51 through the replenishing screw 53.
In the foregoing description, the agitating/carrying member 58 is assumed to start rotation after the toner sensor 56 detects a toner absent state, but the agitating/carrying member 58, being formed by a sheet material and not unnecessarily forcing the toner into the toner sub-container 51, may also be rotated even before the detection of the toner absent state.
Also in case the toner sensor 56 does not detect a toner present state even after a sufficiently long rotation of the agitating/carrying member 58 of the main toner container 57, it can be judged that the toner is replenished into the toner sub-container 51, namely that the toner is absent also in the main toner container 57, whereupon the toner absent state is informed to the user by display means such as an operation panel.
The main toner container 57 may be constructed to be detachable from the apparatus or fixed to the apparatus. In case of the detachable construction, the main toner container 57 is generally called a toner cartridge, and, when the toner is exhausted, the toner replenishment is achieved by replacing the entire main toner container 57. Also the fixed construction, the toner is directly replenished to the main toner container 57 from another toner container.
The replenishing screw 53 is rotated by the drive means 54, with a number of rotations (rotation frequency) or a rotation time selected according to a toner amount required by the developing apparatus, and the rotation is stopped when the number of rotations or the rotation time thus selected is reached, whereby the toner in an amount requested by the developing apparatus is carried and replenished into the developing container. A toner carrying amount per a turn or per a unit time is determined in advance as a constant according to the size of the toner replenishing screw, so that there is enabled a control of calculating the number of rotations or the rotation time according to the requested amount.
Since a toner carrying amount by the screw is proportional to the number of rotations of the screw, a control by the rotation time assumes that the drive means for the screw is capable of always rotating the screw with a constant speed. On the other hand, a control by the number of rotations is possible, even when the rotation speed of the screw is not constant, by providing means which counts the number of rotations of the screw.
In FIGS. 7A and 7B, for the ease of understanding, the photosensitive drum 1 and the developing container 41 has a longitudinal direction perpendicular to the plane of the drawing while the toner sub-container 51, the replenishing screw 53 and the main toner container 57 has a longitudinal direction parallel with the plane of the drawing, but such longitudinal directions are usually provided in parallel.
In the following, there will be explained a driving mechanism for the developer replenishing apparatus 50.
FIG. 8 schematically shows the configuration of a driving mechanism 200 for the developing apparatus 4 and the developer replenishing apparatus 50, similar to that disclosed in Japanese Patent Application Laid-open No. 2000-267419.
As explained in the foregoing, the developing apparatus 4 is capable, by a developer contained therein, of developing an electrostatic image on the photosensitive drum 1 into a visible image. The developing apparatus 4 is provided with a developing screw 44 and an agitating screw 45 constituting developer agitating means which agitates and carries the developer in the developing apparatus 4. Also the developer replenishing apparatus 50 is provided, as described above, with a toner sub-container 51 constituting a first developer container for storing toner to be replenished to the developing apparatus 4, a replenishing screw 53 constituting first replenishing means for discharging the toner from the toner sub-container 51 and replenishing it to the developing apparatus 4, a main toner container 57 constituting a second developer container storing the toner to be replenished to the toner sub-container 51, and an agitating/carrying member 58 constituting second replenishing means for discharging the toner from the main toner container 57 and replenishing it to the toner sub-container 51.
The driving mechanism 200 for the developer replenishing apparatus 50 is provided with a motor 80 constituting rotation drive means which is capable of transmitting a driving power to the replenishing screw 53 and the agitating/carrying member 58, and a drive gear train 70 constituting rotation transmitting means which is capable of transmitting the rotation of the motor 80 to the replenishing screw 53 and the agitating/carrying member 58. The drive gear train 70 includes switch means which is capable of switching in at least two states, namely a first state capable of transmitting the rotation of the motor 80 to the replenishing screw 53 and a second state capable of transmitting it to the agitating/carrying member 58.
More specifically, the drive gear train 70 includes a first drive gear 73a at the side of the motor 80 and a second drive gear 73b engaging with the first drive gear 73a, and the second drive gear 73b selectively engages with a first intermediate gear 71 for transmitting the driving power to the replenishing screw 53 or with a second intermediate gear 72 for transmitting the driving power to the agitating/carrying member 58.
The first intermediate gear 71 transmits the driving power to a replenishing screw driving gear 54 constituting drive means for the replenishing gear 53, while the second intermediate gear 72 transmits the driving power to an agitating/carrying member driving gear 59 constituting drive means for the agitating/carrying member. The second gear 73b is rotatably supported by a lever 73c, rotatably articulated about the center of the first gear 73a. Also the motor 80 is rotatable in the forward and reverse directions, and control means 90 controls rotation of the motor 80 in the forward or reverse direction and stopping thereof.
In the aforementioned configuration, when the motor 80 is rotated in a direction A1 in FIG. 8, the lever 73c rotates in a direction A2 whereby the second drive gear 73b transmits the driving power to the first intermediate gear 71. On the other hand, when the motor 80 is rotated in a direction B1, the lever 73c rotates in a direction B2 whereby the second drive gear 73b transmits the driving power to the second intermediate gear 72. As a result, when the motor 80 rotates in the direction A1, the replenishing screw 53 rotates while the agitating/carrying member 58 is stopped. Also when the motor 80 rotates in the direction B1, the agitating/carrying member 58 rotates while the replenishing screw 53 is stopped.
In this manner, the drive gear train 70, owing to the presence of the lever 73c, can be switched to a first state capable of transmitting the rotation of the motor 80 to the replenishing screw 53 and a second state capable of transmitting the rotation of the motor 80 to the agitating/carrying member 58, by the switching of the rotating direction of the motor 80 by the control means 90.
In this example, as explained in the foregoing, the first drive gear 73a, the second drive gear 73b, the lever 73c, and the control means 90 which control the forward/reverse rotation of the motor 80 constitute switching means which is capable of switching between the first state and the second state mentioned above.
In the aforementioned configuration, in case of rotating the replenishing screw 53 for toner replenishing from the toner sub-container 51 to the developing apparatus 4, the motor 80 is rotated in the direction A1 whereby the replenishing screw 53 can be rotated while the agitating/carrying member 58 is stopped. Also in case of rotating the agitating/carrying member 58 for toner replenishing from the main toner container 57 to the toner sub-container 51, the motor 80 is rotated in the direction B1 whereby the agitating/carrying member 58 can be rotated while the replenishing screw 53 is stopped.
Thus a single motor can achieve the replenishing operation and the agitating operation thereby realizing simplification, compactization and cost reduction of the image forming apparatus, as described in Japanese Patent Application Laid-open No. 2000-267419.
FIG. 9 shows a driving layout of a developing apparatus 4 and a developer replenishing apparatus 50 in each image forming station P (PY, PM, PC, PK) in a four-unit tandem image forming apparatus 100. In each of the first, second, third and fourth colors, the developing apparatus 4, the developer replenishing apparatus 50 and the driving mechanism 200 (200Y, 200M, 200C, 200K) therefore have configurations which are the same as those shown in FIG. 8. A full-color printing is made possible by connecting the developing apparatuses 4 and the developer replenishing 50 of four colors as shown in FIG. 9.
In this system, images of respectively colors are superposed by a movement of an intermediate transfer member (intermediate transfer medium) 7 or a recording material (recording paper) in a direction indicated by an arrow, so that the image forming operations of the respective colors are respectively delayed by a time required by the intermediate transfer member 7 or the recording material to travel over a distance Q indicated in the drawing.
The photosensitive drum 1 (1Y, 1M, 1C, 1K) is rotated constantly as it is in contact with the recording paper or the intermediate transfer member, but the agitating screw and the developing screw as the developer agitating means in the developing apparatus 4 are usually rotated only during a necessary period within the image forming operation, in order to minimize the deterioration of the developer. However, a toner replenishing operation from the toner sub-container to the developing apparatus in a state where the agitating screw and the developing screw in the developing apparatus 4 are stopped may cause a stagnation of the replenished toner in the vicinity of the supply aperture, thereby causing a toner clogging or an uneven T/C ratio in the developing apparatus, so that the toner replenishing operation from the toner sub-container to the developing apparatus has to be conducted in a state where the agitating screw and the developing screw in the developing apparatus 4 are rotated.
FIG. 10 indicates a rotating period of the agitating screw and the developing screw in the developing apparatus, and T therein corresponds to a time of travel of the recording paper or the intermediate transfer medium over the distance Q shown in FIG. 9. Therefore, as shown in FIG. 10, while the agitating screw and the developing screw in the developing apparatus of each color are rotated, the corresponding motor rotates in the direction A1 to rotate the replenishing screw as the toner replenishing means in the developer replenishing apparatus thereby executing a toner replenishing operation from the toner sub-container to the developing apparatus, and the motor is rotated in the direction B1 suitably in other periods to execute an agitating operation.